This invention relates to a technique for the purification and disinfection of water, and more particular to a system and method for the purification and disinfection of water by a treatment including electrical discharge applied across a water stream.
A significant amount of research and development has been undertaken in recent years towards environmental clean-up operations, and in particular to the purification and decontamination of ground water, waste water, and drinking water. A variety of techniques have been used in the prior art to destroy or remove contaminating and toxic materials such as trace organic and inorganic compounds; substances which produce color, taste and odor; pathogenic bacteria; and harmful suspended materials.
These techniques include the use of shock waves created by ultrasonic vibrations and exposing the water to ultraviolet radiation (see, for example, U.S. Pat. No. 6,071,473 to Darwin; U.S. Pat. No. 5,230,792 to Sauska and EP 959046 to Yoshinaga et al.).
Electricity has also been employed as a decontamination agent, such as by introducing positively charged ions into a water stream to cause coagulation and separation of particles, and by the passing of electric current within a fluid chamber (see, for example, U.S. Pat. No. 4,917,782 to Davies; U.S. Pat. No. 5,531,865 to Cole; U.S. Pat. No. 6,346,197 to Stephenson; and U.S. Pat. No. 6,331,321 to Robbins). In this case, the current flowing between the anode and cathode has a toxic effect on microorganisms nearby.
One of the common methods for water disinfection is the use of chlorine as a disinfectant, which is readily available and can be rather easily employed (see, for example, U.S. Pat. No. 4,051,034 to Amon; U.S. Pat. No. 5,039,423 to Kelley; U.S. Pat. No. 5,141,652 to Moore and U.S. Pat. No. 6,296,744 to Djeiranishvili). Chlorine diffuses through the cell wall of the bacterium and operates by disrupting the outer membrane of the cellular organisms, causing organic cellular internal material to spill into the water. However, this method cannot be utilized for purifying water from organic pollutants. The use of chlorine also has its drawbacks because of the formation of compounds that impart a disagreeable taste and odor of the water. In addition, Apart from the unpleasant odor and taste, chlorine also may increase corrosion of water supply pipelines. Additionally, some of chlorine compounds (e.g., trichlorethylene and trihalomethanes), which are also frequently present in the water, are potentially toxic and may pose health hazards.
The utilization of ozone for the purification and disinfection of water is a known and effective technique (see, for example, U.S. Pat. No. 4,352,740 to Grader et al.; U.S. Pat. No. 4,382,044 to Baumgartner; U.S. Pat. No. 4,767,528 to Sasaki et al.; U.S. Pat. No. 5,266,216 to Agueda; U.S. Pat. No. 5,683,576 to Olsen; U.S. Pat. No. 5,711,887 to Gastman et al.; U.S. Pat. No. 6,068,778 to Steiner at al; U.S. Pat. No. 6,146,524 to Story U.S. Pat. No. 6,419,831 to Wang; and U.S. Pat. No. 6,402,945 to Swales et al.). However, it has not yet come into widespread use, such as the general acceptance and widespread use of chlorine.
In recent years, there has been an increased interest in the use of ozone in view of its powerful oxidizing properties and almost instantaneous action, as well as the absence of the formation of a permanent residual material. In particular, ozone has the advantage over chlorine in that it kills bacteria on contact much faster than chlorine and destroys some viruses that are not effected by chlorine. In addition, ozone destroys algae, fungus, mold and yeast spores, oxidizes oils and sulfur, and precipitates metals, e.g., iron, aluminum and manganese. Furthermore, in swimming pool purification systems, the need of periodically adding chlorine to the water and the generally unpleasant effects of chlorine on the eyes and nose make an ozone purification system particularly attractive.
The utilization of hydrogen peroxide injection is also known in the art. This technique in combination with ultraviolet radiation provides for the creation of the xe2x80x94OH radicals necessary to combine with the organic compounds. Notwithstanding that this technique provides effective purification, it did not receive a broad application, mostly due to the strict requirement for high purity hydrogen peroxide and the effects of the inorganic contamination of the surface of ultraviolet lams.
Various techniques for water purification containing organic concomitants based on contacting the water with ozone in the presence of various mixed catalysts are described in U.S. Pat. No. 4,029,578 to Turk; U.S. Pat. No. 5,620,610 to Ishii; U.S. Pat. No. 6,149,820 to Pedersen; and U.S. Pat. No. 6,251,264 to Tanaka.
In particular, the heterogeneous catalyst utilized in U.S. Pat. No. 4,029,578 comprises water insoluble salts, for example, insoluble carbonate, sulfate, oxide, halide or sulfide of such metals as copper, cadmium, and group VIII metals, etc.
According to U.S. Pat. No. 6,149,820, the water enriched with ozone is passed through a catalyst, consisting of activated carbon as the carrier for metal oxides including iron oxide, cobalt oxide, nickel oxides, manganese oxide. Furthermore, the catalyst can contain one or more of the noble metals, e.g., platinum or palladium.
A method for water purification described in U.S. Pat. No. 6,251,264 includes the steps of dispersing photo-catalyst particles and an inorganic coagulant and oxidizing the organic matter contained in the water by activating the photo-catalyst particles by irradiating them with light.
A variety of techniques are known in the art which utilize a filtration process. For example, a filter can be made of a combination of a porous media, activated carbon and ion exchange filters. One of the disadvantages of this water purification technique is that the structure of the filter provides a breeding ground for microorganisms, thereby multiplying the danger. Such techniques, especially effective when used in combination with ultraviolet irradiation, ozonation and chlorination can effectively purify and disinfect the water (See, for example, U.S. Pat. No. 4,077,877 to Orensten et al.; U.S. Pat. No. 5,236,595 to Wang; U.S. Pat. No. 5,536,403 to Sugimoto; U.S. Pat. No. 5,728,305 to Hawkinson; U.S. Pat. No. 5,766,488 to Uban, et al.; and U.S. Pat. No. 6,358,407 to Liao, et al.). However, since activated carbon filters as well as other biological and chemical filters are extremely costly and must be changed regularly, these techniques did not receive wide popularity.
A technique is known in the art, sometimes under the name electro-hydraulics, which utilize high-energy electrical discharge into a volume of liquid for the purpose of disinfecting water, changing chemical constituents and recovering metals and other substances from liquids or slurries (see, for example, U.S. Pat. No. 3,366,564 to Allen; U.S. Pat. No. 3,402,120 to Allen et al.; and U.S. Pat. No. 4,957,606 to Juvan). According to this technique, an electro-hydraulic shock wave within the liquid, intensive light radiation and thermo-chemical reactions are initiated by arc discharge into a spark gap formed by the electrodes immersed in the liquid. One of the drawbacks of this technique is associated with the fact that in the repeated discharging of a high-energy electrical arc across the gap between electrodes, the electrodes are rather rapidly eroded and burned up. Similarly, switching components are consumed by burnup.
U.S. Pat. No. 5,464,513 to Goriachev and U.S. Pat. No. 5,630,915 to Green et al. describes a water purification technique which concurrently uses a synergistic combination of pulsed mechanical shock waves, ultraviolet radiation, and ionization of the water stream, as disinfecting and purification actions within the water to be treated. The water treatment system of this technique includes a pair of electrodes extending transversely across and through a discharge chamber. Contaminated water is introduced into the chamber through an intake port where it passes either through or proximate to the discharge area. A pulse power unit delivers a rapid sequence of arc inducing electrical pulses across the electrodes, thereby producing a series of electric discharge arcs across the discharge area between the electrodes. The arcs are of sufficient energy whereby a plasma inducing arc is sustained through the water across the electrodes, generating lethal levels of ultraviolet radiation, as well as mechanical shock waves having the capacity of directly killing microorganisms and weakening others. Furthermore, molecules of water proximate to the discharge area are broken down into excited radicals, including hydroxyl ions and free oxygen, which combine with organic chemicals to eliminate them from the water stream.
RU Pat. No. 2136600 to Boyev et al. describes a technique for water purification by means of barrier high energy electric discharges formed as a result of the application of a pulsed electric field applied between the electrodes to an air-water mixture formed from water jets and drops. The pulsed electric filed is characterized by the pulse duration shorter than 0.5 microseconds, the slope of the pulse""s front greater than 109 V/s and the amplitude of the field strength being in the range of 20-100 kV/cm. For this purpose, the high voltage pulses are applied with the frequency higher than 50 Hz. The frequency magnitude f is selected from the condition       f    ≥          50      ⁢              xe2x80x83            ⁢              v        h              ,
where v is the speed of the water flux and h is the height of the electrode system. The values of the pulse parameters were chosen such that the conductivity of the system at these pulse conditions is significantly small, i.e., the water is an electrical insulator.
The electrode system includes a set of electrodes implemented in the form of two combs. One of the combs is coupled to the generator of the high voltage pulses, while the electrodes of the other comb are grounded. The electrodes are covered by an electrical insulating barrier in the form of tubes made of quartz glass.
Various configurations of the electrode system that can be utilized in the device for water purification are disclosed in RU Pat. Nos. 2136601; 2136602 and 2152359 to Ryazanov et al.
In particular, RU Pat. No. 2136601 describes a discharge chamber including a high voltage and grounded electrodes implemented in the form of a volume grid wherein the high voltage electrode is arranged between the grounded electrodes.
RU Pat. No. 2136602 describes an electrode system wherein the grounded electrode is in the form of a cylinder, while the high voltage electrode is in the form of a cylindrical brush which is housed within the ground electrode.
RU Pat. No 2152359 describes a discharge chamber including a high voltage electrode is implemented in the form of a volume grid, while the grounded electrode is configured as a perforated partition implemented in the form of hollow cylinders.
Despite the extensive prior art in the area of water decontamination techniques, there is still a need in the art for, and it would be useful to have, a novel system and method for water purification and disinfection which is effective both on microorganisms as well as on organic chemicals and chemical toxins.
In addition, it would be advantageous to have an effective system capable to remove substances which produce color, taste and odor as well as to improve organoleptic properties of the water.
The present invention satisfies the aforementioned need by providing a novel system for purification and disinfection of water containing contaminates. The system includes an aeration column, a first intermediate tank, a first mechanical filter, an electric discharge device, a second intermediate tank, a second mechanical filter and a sorption filter.
The aeration column is configured for continuous mixing the water with air and ozone-air mixture The first intermediate tank is configured for receiving the water flowing downwardly from the aeration column and treating the water with coagulant materials in the presence of ozone-air mixture. The first mechanical filter is coupled to the first intermediate tank and arranged for purification of the water from coagulated particles formed in the first intermediate tank. The electric discharge device is arranged downstream of the first mechanical filter and arranged for treatment of the water by electric discharges in an air medium. The second intermediate tank is configured for receiving the water flowing downwardly from the electric discharge device and treating the water with coagulant materials in presents of ozone-air mixture. The second mechanical filter is coupled to the second intermediate tank and arranged for purification of the water from coagulated particles formed at least in the second intermediate tank. The sorption filter is arranged downstream of said second mechanical filter and arranged, inter alia, for purification of the water from organic compounds.
According to one embodiments of the invention, the electric discharge device comprises a discharge chamber bounded by a case. The case includes a water inlet manifold, a gas inlet manifold, a voltage-operated electrode, a grounded electrode; a high voltage pulse power source; a water discharge manifold and a gas discharge manifold adapted for discharging unreacted ozone-air mixture.
The water inlet manifold is arranged for delivering the water into the discharge chamber. The gas inlet manifold is arranged for delivering an oxygenated gas into the discharge chamber. The voltage-operated electrode is insulated from the case by means of a bushing. The grounded electrode is connected to the case, and adapted for bearing the water. According to this embodiment of the invention, the water has a free water surface spaced from the voltage-operated electrode. The high voltage pulse power source is coupled to the voltage-operated electrode and the grounded electrode and configured to supply high voltage pulses thereto. The high-voltage pulses are sufficient to generate a crown electric discharge in the volume between the voltage-operated electrode and the free water surface for producing ultraviolet radiation, ozone, atomic oxygen, excited oxygen molecules, electrons and ions above the water surface, together with OHxe2x88x92 radicals, peroxides and protoxides in the water volume. The water discharge manifold is configured for discharging the water treated by the electric discharge. The gas discharge manifold is adapted for discharging unreacted ozone-air mixture.
The amplitude of the voltage pulses is higher than 10 kV (preferably, in the range of 30 kV to 50 kV);
The pulse duration (i.e., pulse length) is shorter than 0.5 microseconds (preferably, in the range of 50 to 200 nanoseconds);
The duration of the pulse""s front (i.e., pulse rise time) is shorter than 50 nanoseconds (preferably, in the range of 10 to 20 nanoseconds);
The pulse repetition frequency is higher than 200 Hz (preferably, in the range of 500 to 1500 Hz).
According to one embodiment of the invention, the voltage-operated electrode is configured in the form of a volume grid, while the grounded electrode is in the form of inclined plate, along which the water flows down by gravity. The plate is arranged substantially parallel to the voltage-operated electrode.
According to another embodiment of the invention, the voltage-operated electrode is configured in the form of a volume grid, while the grounded electrode is in the form of a bowl bearing the water. The grounded electrode is arranged below the voltage-operated electrode and connected to the case by means of the water inlet manifold.
According to still another embodiment of the invention, the voltage-operated electrode is implemented as a set of rings connected to a stem via connecting links, while the grounded electrode is configured in the form of a truncated cone. According to this embodiment, the water flows down by gravity along the truncated cone connected to the case. The rings are arranged concentrically to the truncated cone.
The system according to the present invention using the high-energy electric discharge device has a rather high efficiency, with relatively low component cost, very low down time, relatively low power consumption and low plant cost for a relatively high volume throughput.
The aforementioned need is also satisfied by providing a method for purification and disinfection of water containing contaminates. According to one embodiment of the invention, the water is firstly aerated by continuous mixing the water with air and ozone-air mixture. The water obtained after the aeration is treated with coagulant materials. The treating of the water with coagulant materials is carried out in a medium of the ozone-air mixture. Further, the water is filtered from coagulated particles. Thereafter, the water is treated by electric discharges in an air medium. The water is then treated again with coagulant materials. Finally, the water is filtered from remaining contaminates. The final filtering of the water includes transferring the water through a mechanical filter, and thereafter through a sorption filter.
Thus, in accordance with one broad aspect of the invention, there is provided a system for purification and disinfection of water containing contaminates, comprising:
(a) an aeration column configured for continuous mixing the water with air and ozone-air mixture;
(b) a first intermediate tank configured for receiving the water flowing downwardly from said aeration column and treating the water at least with coagulant materials;
(c) a first mechanical filter coupled to said first intermediate tank and arranged for purification of the water from coagulated particles formed in said first intermediate tank;
(d) an electric discharge device downstream of said first mechanical filter arranged for treatment of the water by electric discharges in an air medium;
(e) a second intermediate tank configured for receiving the water flowing downwardly from said electric discharge device and treating the water at least with coagulant materials;
(f) a second mechanical filter coupled to said second intermediate tank and arranged for purification of the water from coagulated particles formed at least in said second intermediate tank.
In accordance with another broad aspect of the invention, there is provided an electric discharge device for water treatment by electric discharges comprising a discharge chamber bounded by a case including:
(i) a water inlet manifold for delivering the water into the discharge chamber;
(ii) a gas inlet manifold for delivering an oxygenated gas into the discharge chamber;
(iii) a voltage-operated electrode insulated from the case by means of a bushing;
(iv) a grounded electrode connected to the case and adapted for bearing the water, said water having a free water surface spaced from said voltage-operated electrode;
(v) a high voltage pulse power source coupled to said voltage-operated electrode and said grounded electrode and configured to supply high voltage pulses thereto;
(vi) a water discharge manifold configured for discharging the water treated by said electric discharge;
(vii) a gas discharge manifold adapted for discharging unreacted ozone-air mixture.
In accordance with still another broad aspect of the invention, there is provided a method for purification and disinfection of water containing contaminates, comprising the steps of:
(a) aerating the water by continuous mixing the water with air and ozone-air mixture;
(b) treating the water obtained after step (a) with coagulant materials;
(c) filtering the water after obtained step (b) from coagulated particles;
(d) treating the water by electric discharges in an air medium;
(e) treating the water obtained after step (d) with coagulant materials; and
(f) filtering the water after obtained step (e) from remaining contaminates.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows hereinafter may be better understood. Additional details and advantages of the invention will be set forth in the detailed description, and in part will be appreciated from the description, or may be learned by practice of the invention.